I speculate that the majority of banks/lenders will adhere to the Safe Harbor guidelines, under which less borrowers will be eligible for mortgages.
Some borrowers will funnel towards FHA, which generally costs more when you factor in the PMI requirements.
There will probably be niche providers who offer private-label financing as well. My guess is that the cost will be higher for these loans as well since there will be more risk to the lender...they won't have the ability to sell the loans to Fannie or Freddie.
Our government is putting these guidelines in place to "protect the consumer" so I have no doubt they will screw things up and this will wind up making things tougher on consumers as well as hard working loan officers whose livelihoods depend on being honest and ethical and helping their customers obtain mortgages.
We shall see...